linux-kernel - [PATCH 3.18 087/183] clk: Really fix deadlock with mmap

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Message-Id: <20150125180813.963008758@linuxfoundation.org>
Date:	Sun, 25 Jan 2015 10:06:49 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Russell King <rmk+kernel@....linux.org.uk>,
	Stephen Boyd <sboyd@...eaurora.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Michael Turquette <mturquette@...aro.org>
Subject: [PATCH 3.18 087/183] clk: Really fix deadlock with mmap_sem

3.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Stephen Boyd <sboyd@...eaurora.org>

commit 89f7e9de59bf3e3cda2e00de12c66db22675a7cf upstream.

Commit 6314b6796e3c (clk: Don't hold prepare_lock across debugfs
creation, 2014-09-04) forgot to update one place where we hold
the prepare_lock while creating debugfs directories. This means
we still have the chance of a deadlock that the commit was trying
to fix. Actually fix it by moving the debugfs creation outside
the prepare_lock.

Reported-by: Russell King <rmk+kernel@....linux.org.uk>
Fixes: 6314b6796e3c "clk: Don't hold prepare_lock across debugfs creation"
Signed-off-by: Stephen Boyd <sboyd@...eaurora.org>
Reviewed-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Michael Turquette <mturquette@...aro.org>
[mturquette@...aro.org: removed lockdep_assert]
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/clk/clk.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -240,7 +240,6 @@ static const struct file_operations clk_
 	.release	= single_release,
 };
 
-/* caller must hold prepare_lock */
 static int clk_debug_create_one(struct clk *clk, struct dentry *pdentry)
 {
 	struct dentry *d;
@@ -1944,7 +1943,6 @@ int __clk_init(struct device *dev, struc
 	else
 		clk->rate = 0;
 
-	clk_debug_register(clk);
 	/*
 	 * walk the list of orphan clocks and reparent any that are children of
 	 * this clock
@@ -1979,6 +1977,9 @@ int __clk_init(struct device *dev, struc
 out:
 	clk_prepare_unlock();
 
+	if (!ret)
+		clk_debug_register(clk);
+
 	return ret;
 }
 


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